The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
An electronically lockable differential may be referred to as an “e-Locker”. The e-Locker increases the traction capability of a vehicle when the vehicle is being driven off-road over uneven. Rock climbing is a particular example of off-road driving where an e-Locker is helpful.
However, when the vehicle is driven on the road, the vehicle's differential should not be locked. Locking the differential when driving on paved roads may disable safety critical systems of the vehicle such as an antilock braking system (ABS) and electronic stability control (ESC). Operating a vehicle on paved roads with the differential locked may also adversely affect the steering of the vehicle.
An e-Locker may include a solenoid coil which moves a linear actuator to lock the differential gear set in the drive axle. A spring may be attached with the actuator so that when the coil is de-energized, the actuator returns to its disengaged position, and thus place the e-Locker in its disengaged state. However, under certain circumstances the spring force may not be sufficient to overcome the friction exerted by the differential locker. When the driver begins a lane change maneuver or a turn on a paved dry road, the vehicle may behave differently if the e-Locker is still engaged. This is because with the e-Locker engaged, the axles associated with both of the driven wheels will be forced to turn at the same speed. While changing lanes or making a turn, the outside wheel needs to rotate faster than the inside wheel. Therefore, it is important for the status of the e-Locker to be known to the vehicle's controller so that the controller can take the appropriate control action.
It is difficult to determine when the e-Locker is stuck because of the difficulty in incorporating a position sensor inside the differential locker assembly. Differential wheel speed and steering angle information are often used to determine if the actuator of the e-Locker actuator is stuck. Therefore, the vehicle typically has to go through a few maneuvers before the ECU is able to diagnose the status of the e-Locker.